Peritoneal dialysis in acute renal failure in canines : A review

Peritoneal dialysis is a technique whereby infusion of dialysis solution into the peritoneal cavity is followed by a variable dwell time and subsequent drainage. During peritoneal dialysis, solutes and fluids are exchanged between the capillary blood and the intraperitoneal fluid through a biologic membrane, the peritoneum. Inadequate renal function leads to disturbance in the removal of the extra fluid and waste products. It removes the waste product and extra fluid from the body in renal failure in small animal practice. Peritoneal dialysis is more accessible, more affordable and easier to administer to the small animal patient. The most common indication for peritoneal dialysis in dogs is acute renal failure (ARF). Peritoneal dialysis is an important therapeutic tool for mitigating clinical signs of uremia and giving the kidneys time to recover in cats with acute kidney injury when conventional therapy is no longer effective.


Introduction
between the peritoneal capillary blood and dialysate.The ratio of solute concentrations in dialysate and Peritoneal dialysis is a modality of renal plasma at specific times during the dwell signifies the replacement therapy that is commonly used in human extent of solute transport.Creatinine and urea medicine for treatment of chronic kidney disease and clearance rates are the most commonly used indices of end-stage kidney failure.Peritoneal dialysis uses the dialysis adequacy in clinical settings.Contributions of peritoneum as a membrane across which fluids and residual renal clearances are significant in uremic solutes are exchanged.In this process, determining the adequacy of dialysis (Flessner et al., dialysate is instilled into the peritoneal cavity and, 1985).through the process of diffusion and osmosis, water, toxins, electrolytes, and other small molecules, are Mode of action allowed to equilibrate (Cooper and Labato, 2011 ).
Hemodialysis is a life-saving medical modality Peritoneal dialysis uses the peritoneum as a semi that cleanses the blood using an artificial kidney, permeable layer for dialysis in which excess water, called a dialyzer.Hemodialysis uses contact between ions and solute in the blood pass through a semi the patient's blood and the semipermeable membrane permeable membrane to a sterile solution which is of the extracorporeal dialyzer to remove compounds known as dialysate via diffusion, osmosis and such as blood urea nitrogen, creatinine, electrolytes, filtration.The three-layered peritoneal membrane minerals, anions, cations, certain drugs and toxins, and consists of 1) the mesothelium, a continuous monolayer excess fluid from the bloodstream.The extracorporeal of flat cells, and their basement membranes; 2) a very dialyzer distinguishes hemodialysis from peritoneal compliant interstitium; and 3) the capillary wall, dialysis, which uses a patient's peritoneum as the consisting of a continuous layer of mainly nondialysis membrane (Bloom and Labato, 2011).fenestrated endothelial cells, supported by a basement The capillary endothelial cell membrane is membrane.The mesothelial layer is considered to be permeable to water through aquaporins (radius of less of a transport barrier to fluid and solutes, approximately 0.2 to 0.4 nm) (Pannekeet et al., 1996).
In addition, small solutes and water are transported including macromolecules, than is the endothelial layer (Clough and Michel, 1988).Solute transport through ubiquitous small pores (radius of approximately 0.4 to 0.55 nm).Sparsely populated rates are assessed by the rates of their equilibration large pores (radius of approximately 0.25 nm, perhaps the absence of ultrafiltration and when the rate of mainly venular) transport macromolecules passively.solute accumulation in the dialysis solution is zero Diffusion and convection move small molecules (Nolph et al., 1979).through the interstitium with its gel and sol phases, Conventional peritoneal dialysis solutions contain glucose, lactate, sodium, potassium, and which are restrictive owing to the phenomenon of calcium in differing concentrations.Lactate, exclusion.The lymphatic vessels located primarily in bicarbonate or a combination of the two are used to the subdiaphragmatic region drain fluid and solutes make pH neutral dialysate solutions.Acetate should be from the peritoneal cavity through bulk transport.The avoided because it is associated with loss of extent of lymph drainage from the peritoneal cavity is a subject of controversy owing to the lack of a direct ultrafiltration and sclerosing peritonitis.Glucose is the method to measure lymph flow (Wade et al., 1956).
most commonly used osmotic agent and draws fluid Dialysis solution contains electrolytes in across the peritoneal membrane.Newer solutions use physiologic concentrations to facilitate correction of alternative osmotic agents including Icodextrin acid-base and electrolyte abnormalities.High concen-(glucose polymers), for sustained ultrafiltration, or trations of glucose in the dialysis solution generate amino acids to address an assumed positive effect on ultrafiltration in proportion to the overall osmotic nutritional status (Gokal and Mallick, 1999).These gradient, the reflection coefficients of small solutes alternative solutions can only be used in a single daily relative to the peritoneum, and the peritoneal membrane exchange or intermittently and have not been hydraulic permeability.Removal of solutes such as clinically evaluated in veterinary medicine.Dialysate urea, creatinine, phosphate, and other metabolic end choices include commercial dialysate (e.g., Dianeal) products from the body depends on the development which comes prepared as a 1.25%, 2.5% or 4.5% of concentration gradients between blood and glucose solution, or home-made alternatives, which intraperitoneal fluid, and the transport is driven by the include lactated ringers solution (LRS), 0.9% sodium process of diffusion.The amount of solute removal is a chloride, and 0.45% sodium chloride based on function of the degree of its concentration gradient, the availability as well as the electrolyte status of the molecular size, membrane permeability and surface patient.Dextrose is added to these solutions to make a area, duration of dialysis, and charge.Ultrafiltration 1.25%, 2.5% or 4.5% solution.The concentration of adds a convective component proportionately more dextrose depends on the hydration status of the patient important as the molecular size of the solute increases.with higher dextrose concentrations achieving The peritoneal equilibration test is a clinical tool used improved ultrafiltration and water removal.A 4.5% to characterize the peritoneal membrane transport solution should only be used when patients are fluid properties (Twardowski et al., 1987).
overloaded, and a 1.25% solution is generally Solute transport rates are assessed by the rates of adequate in normovolemic patients.Potassium, their equilibration between the peritoneal capillary magnesium, and calcium can be added to the dialysate blood and dialysate.The ratio of solute concentrations based on the patient's electrolyte status.The potassium in dialysate and plasma at specific times during the concentration in LRS is 4 mEq/L, this is generally low dwell signifies the extent of solute transport.The enough to be used in hyperkalemic patients while still fraction of glucose absorbed from the dialysate at correcting moderate to severe hyperkalemia.If normal specific times can be determined by the ratio of saline is used, sodium bicarbonate should be added as dialysate glucose concentrations at specific times to a buffer solution at 30-45 mEq/L (Mathews, 2006).the initial level in the dialysis solution.Tests are Standard commercial dialysate solutions are standardized for the following: duration of the designed to remove urea, creatinine, potassium and preceding exchange before the test; inflow volume; phosphate from the plasma into the dialysate by the process of diffusion.A variety of dialysate solutions positions during inflow, drain, and dwell; durations of can be used with differing osmolalities on a case by-inflow and drain; sampling methods and processing; case basis depending on the ?uid balance of the and laboratory assays (Ahearn and Nolph, 1972).
patient.Fluid and solutes move across the peritoneum Creatinine and urea clearance rates are the most by diffusion, ultra?ltration and convection.Urea and commonly used indices of dialysis adequacy in potassium diffuse across the peritoneal membrane clinical settings.Contributions of residual renal quickly, whereas creatinine and phosphorus take clearances are significant in determining the adequacy longer to equilibrate (Zabetakis et al., 1993). of dialysis.The mass-transfer area coefficient During peritoneal dialysis, hyperosmolar (MTAC) represents the clearance rate by diffusion in glucose solution generates ultrafiltration by the process peritoneal membrane permeability (P) and effective of osmosis.Water movement across the peritoneal peritoneal membrane surface area (S) (Pyle, 1981).membrane is proportional to the transmembrane Thus, when both capillary blood and dialysate flows pressure, membrane area, and membrane hydraulic are infinite, the clearance rate is directly proportional permeability.The transmembrane pressure is the sum to the effective peritoneal surface area and inversely of hydrostatic and osmotic pressure differences proportional to the overall membrane resistance.between the blood in the peritoneal capillary and However, infinite blood and dialysate flows cannot be dialysis solution in the peritoneal cavity (Wolf et al., achieved, and the maximum clearance rate is 1992).Net transcapillary ultrafiltration defines net unattainable.The closest measurable value, the fluid movement from the peritoneal microcirculation MTAC, was introduced.The MTAC represents an into the peritoneal cavity primarily in response to instantaneous clearance without being influenced by osmotic pressure.Net ultrafiltration would equal the ultrafiltration and solute accumulation in the dialysate resulting increment in intraperitoneal fluid volume if it (Farrell and Randerson, 1980).The MTAC is were not for peritoneal reabsorption, mostly through measured over a test exchange during which at least the peritoneal lymphatics.Peritoneal reabsorption is two blood and dialysate samples are obtained at continuous and reduces the intraperitoneal volume different dwell times (Pyle et al., 1981).The precision throughout the dwell (Mactier et al., 1987).
of the measurement is enhanced with more data points.The urea clearance is normalized to total body The MTAC is seldom used clinically; however, it is a water (volume of urea distribution in the body) and is very useful research tool (Garred et al., 1983).expressed as Kt/V.The Kt/Vvalue is a number without Indications a unit (mL/min).During intermittent dialysis, with a The major indication for peritoneal dialysis is dialysate flow rate of 30 mL/min, the typical urea renal failure with oliguria or anuria.It may be indicated clearance is about 18 to 20 mL/min.Increasing the if the blood urea nitrogen (BUN) concentration is dialysate flow rates to 3. 5 Twardowski, 1994).Continuous dialysate flow or hyperthermia (Labato, 2000).techniques using either two catheters or double-lumen catheters also have enhanced the urea clearance rate to Procedure a maximum of 40 mL/min.At these high flow rates, Catheter placement is performed using strict poor mixing, channeling, abdominal pain, and poor aseptic technique and, if possible, in a surgery suite.A drainage limit successful application.Maintaining a urinary catheter should always be placed prior to fluid reservoir in the peritoneal cavity (called tidal placement of a dialysis catheter to prevent bladder peritoneal dialysis) and then replacing only a fraction trauma on insertion (Struijk et al., 1994).As catheters of the intraperitoneal volume rapidly, increases are generally placed in animals with acute renal clearance rates by about 30% compared with the failure, these animals are generally depressed and standard technique using the same doses owing to regardless of technique for catheter placement maintaining fluid-membrane contact at higher (percutaneous or minisurgical approach), mild sedation dialysis-solution flow rates (Di Paolo, 1978, Finkelstein and local anesthesia are frequently sufficient.With the and Kliger, 1979, Twardowski et al., 1990).
patient in lateral or dorsal recumbency the abdomen is The mass-transfer area coefficient (MTAC) clipped from the xiphoid to the pubis and surgically prepared.Administration of a prophylactic dose of a The MTAC represents the clearance rate by first generation cephalosporin is recommended prior diffusion in the absence of ultrafiltration and when the solute accumulation in the dialysis solution is zero to catheter insertion (Boen, 1961).(Randerson, 1980).MTAC is equal to the product of Catheters can be placed via mini surgical approach, laparoscopically, or percutaneously.No dogs (80%) survived to discharge from the hospital.method has proven to be more advantageous.Survival in this study was similar to other studies of Regardless of the technique used, a subcutaneous ARF secondary to leptospirosis with reported survival tunnel is recommended.The catheter can enter the rates of 82% (18/22) in dogs treated conservatively abdomen on midline or via a paramedian approach, at with antibiotics and IV fluids, and 86% (12/14) in dogs the level of the umbilicus.The catheter should be treated with hemodialysis by Lichtenberger (2007).directed caudally and positioned in the lower pelvis.

Conclusion
Catheter placement should be verified by infusing, and easily retrieving, a small volume of dialysate (2-5 ml) Peritoneal dialysis is the process of utilizing the before the catheter is secured (Ash, 2003 and Cowgill, peritoneum as a semipermeable membrane in order to 1995).
move solutes and water between blood in the Patient parameters are monitored daily includes : peritoneal capillaries and ?uid (dialysate) instilled into the peritoneal cavity.Peritoneal dialysis is used (a) perfusion and hydration viz.PCV/TP, blood most frequently in management of acute kidney injury pressure, heart rate, urine output, temperature, CVP; refractory to ?uid therapy, but it also has been used in (b) Electrolytes, BUN, and creatinine; (c) Respiration management of severe metabolic disturbances, acute (respiratory distress can occur from over distention of poisoning with dialyzable substances (e.g.ethylene the abdomen or leakage of dialysate into the pleural glycol, ethanol, barbiturates) and severe temperature cavity); (d) Cytology on effluent dialysate (to monitor extremes.for peritonitis).
to 12 L/h by rapid exchanges greater than 100 mg/dL (35 mmol/L) or the serum increases the urea clearance rate to a maximum of 30 creatinine concentration is greater than 10 mg/dL (884 to 40 mL/min.Beyond this maximum rate, the umol/L) and medical management has failed to elicit a clearance rate begins to decrease owing to the loss of positive response (Lew et al., 2005).